As a sterilization method of container-packaged food, a “retort sterilization method” is comprised of filling food in a container, sealing an opening of the container with a lid material and subsequently transporting the container to a chamber, and performing thermal sterilization with high temperature and pressure steam or compressed hot water, and a “steam injection sterilization method” of filling food in a container and thereafter introducing high temperature and pressure steam therein, and performing thermal sterilization while a heating medium such as steam directly comes in contact with the food. The steam injection sterilization method can be further classified into two types based on the supply system of the lid material. One is a sterilization method of subjecting a container filled with food to thermal sterilization using steam and thereafter sealing an opening of the container with a sterilized lid material which underwent separate sterilization (for example, refer to Patent Documents 1 and 2), and the other is a sterilization method of partially fusion bonding (temporarily sealing) a lid material on a flange portion of a container filled with food, and subsequently performing thermal sterilization by introducing high temperature and pressure steam, and thereafter sealing (main sealing) the lid material with a heat seal bar by fusion bonding it to the flange portion of the container (for example, refer to Patent Document 3).
With the former sterilization method, in addition to a device for sterilizing the container filled with food, a separate device for sterilizing the lid material is required. Meanwhile, with the latter sterilization method, in addition to a sealing device for completely fusion bonding the lid material to the flange portion of the container, a temporary sealing device for partially fusion bonding the lid material to the flange portion of the container is separately required.    Patent Document 1: Japanese Published Unexamined Patent Application Publication No. H09-009937    Patent Document 2: Japanese Published Unexamined Patent Application Publication No. 2005-341922    Patent Document 3: Japanese Published Unexamined Patent Application Publication No. 2005-118004